package com.atguigu.algorithm;

import java.util.Scanner;

public class TheNumOfPizza {
    public static void main(String[] args) {
        Scanner scanner=new Scanner(System.in);
        while(scanner.hasNextInt()){
            int from=scanner.nextInt();
            int to=scanner.nextInt();
            int[] help=new int[to+1];
            help[0]=1;
            help[1]=1;
            for(int i=2;i<help.length;i++){
                help[i]=help[i-1]+help[i-2];
            }
            int sum=0;
            for(int i=from;i<=to;i++){
                sum+=help[i];
            }
            System.out.println(sum);
        }
        //1 1 2 3 5 8 13
    }
}
